Microsoft Windows SSTP: Use-after-free leads to remote code execution

Summary

A use-after-free flaw (CWE-416) in the Windows Secure Socket Tunneling Protocol (SSTP) allows an unauthenticated remote attacker to execute code over the network. The attack complexity is rated high and no user interaction is required. Systems are only reachable if they run an SSTP listener, typically a Windows Server RRAS VPN endpoint.

Affected

• Windows 10 Version 1607 (below 10.0.14393.9612)
• Windows 10 Version 1809 (below 10.0.17763.9376)
• Windows 10 Version 21H2 (below 10.0.19044.7807)
• Windows 10 Version 22H2 (below 10.0.19045.7807)
• Windows 11 Version 23H2 (below 10.0.22631.7652)
• Windows 11 Version 24H2 (below 10.0.26100.9711)
• Windows 11 Version 25H2 (below 10.0.26200.9711)
• Windows 11 Version 26H1 (below 10.0.28000.3231)
• Windows 11 Version 26H2 (below 10.0.26300.9711)
• Windows Server 2012, including Server Core (below 6.2.9200.26434)
• Windows Server 2012 R2, including Server Core (below 6.3.9600.23470)
• Windows Server 2016 (below 10.0.14393.9612)

Fixed in

• Install the October 2026 security update for each affected branch, at or above the build numbers listed above.
• The KB number for Windows 10 1607 and Server 2016 is not confirmed in these sources. Take it from the MSRC advisory.

Workaround

Unknown. No vendor-provided workaround was found in the sources.

• Third-party guidance suggests disabling SSTP as a tunnel option on RRAS. This is not confirmed by the vendor and would break remote-access VPN clients that depend on SSTP.

Exploitation

• No confirmed exploitation in the wild was found in the sources.
• CISA SSVC: exploitation none, automatable no, technical impact total.
• No public proof of concept was found.

Our recommendation

• Inventory Windows hosts with the SSTP/RRAS role and check their build numbers.
• Check whether Windows 10 1607 and Server 2016 still receive security updates. If not, plan an upgrade or migrate away from SSTP.
• Apply the October 2026 cumulative update to all affected systems, using the KBs listed on the MSRC advisory.
• If patching is delayed, restrict SSTP exposure at the firewall after testing the impact on VPN users.
• Treat exposed SSTP VPN endpoints as high priority.

Public exploits iAttack code is publicly available (PoC on GitHub, Metasploit or Exploit-DB).

PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.

Research sources

• Microsoft Security Update Guide: CVE-2026-85926 msrc.microsoft.com
• SentinelOne Vulnerability Database: CVE-2026-85926 www.sentinelone.com
• Vulners NVD record: CVE-2026-85926 vulners.com
• Vulners CVElist record: CVE-2026-85926 vulners.com
• VulDB: CVE-2026-85926 vuldb.com
• OpenCVE: CVE-2026-85926 app.opencve.io
• Strix: CVE-2026-85926 www.strix.ai
• Vulners PT-2026-87918 (related SSTP RCE context) vulners.com

Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 1 Nov 2026, 19:21.